Why the river you think is healthy and the garden you think is wild are both haunted by an abundance you never experienced, and what shifting baseline syndrome means for anyone trying to bring nature back. Stand on a bridge over a lowland river on a bright morning. The water runs more or less clear. A moorhen picks along the margin, willows lean over the bank, a couple of mallard drift past. It looks, by any ordinary reckoning, like a healthy river. A nice river. The kind of